1. Field of the Invention
The present invention generally relates to shotshells and, more particularly, is concerned with an improved shot wad structure for shotshells which is assembled from components that are adjustable with respect to one another to accommodate a range of different sizes of shot loads or charges in shotshells.
2. Description of the Prior Art
It is conventional practice to provide plastic wad structures for use in shotshells to house the shot charge, obturate combustion gases, and cushion the shot charge when the loaded wad is fired from a shotgun. One wad structure representative of this practice is illustrated and described in U.S. Pat. No. 3,285,174 to V. C. Moehlman et al, which patent issued Nov. 15, 1966 and is assigned to the assignee of the present invention.
Typically, the wad structure has a unitary one-piece construction and is composed of a shot pocket portion, a filler or cushioning portion and an obturating portion. The shot pocket portion is shaped like a cup and includes a cylindrical split sidewall open at the top and closed at the bottom. The obturating portion has a shallow cup-like shape and includes a base with a peripheral flared skirt. The cushioning portion generally includes a series of flexible members which extend between and interconnect the other two portions of the wad structure.
When a shotshell containing the above-described wad structure is loaded in a shotgun and fired, a propellant disposed in the shell tube rearwardly of the obturating portion is consumed and produces high pressure combustion gases. The pressurized gases act upon the obturating portion, causing its skirt to expand outwardly into sealing relationship with the inner surface of the the shell tube and wall of the gun barrel bore. Such sealing increases the compressive forces being generated by the pressurized combustion gases. Since the column of shot pellets contained in the shot pocket portion of the wad structure initially resists forward movement, the compressive forces first compress the cushioning portion of the wad structure. Then, as the wad structure and shot column are propelled out of the shell tube and start to accelerate through the gun barrel, the shot column pushes radially outward toward the wall of the barrel bore and against the sidewall of the shot pocket portion.
Historically, shot pellets have been composed of lead which is much softer than the metal traditionally composing the gun barrel. Therefore, an important objective of the shot pocket portion of the wad structure heretofore has been to prevent contact of the softer shot pellets with the harder barrel in order to prevent leading of the barrel and distortion of the shot pellets. This objective of lead shot protection has been satisfactorily attained by the shot pocket portion design disclosed in the aforesaid patent.
However, due to the toxicity of lead and health concerns about possible retention of lead shot in game intended for human consumption, laws have recently been enacted in many states which substantially limit or even ban the use of traditional lead shot pellets in hunting game and mandate the use of hard materials having little or no known toxicity, such as steel or tungsten. While formerly in the case of lead shot pellets the objective of the shot pocket portion was to protect the softer shot pellets from the harder gun barrel, now in the case of steel shot pellets the new objective is to protect the softer gun barrel from the harder shot pellets. The shot pocket portions of wad structures designed for use with lead shot pellets have proven unable to meet this new objective. The plastic material used heretofore fails to withstand the compressive forces of the hard shot. The shot readily penetrates through the sidewall of the pocket portion and contacts the barrel wall, causing marring or scoring thereof. Merely making the plastic material heavier or thicker or substituting a stronger plastic material has not been found to provide a workable and economical solution to the problem of preventing barrel scoring. Plastic materials that are strong enough to withstand the force of the steel shot are usually expensive and, in some cases, too stiff to allow proper obturation of the propellant gases in cold weather.
This new objective which requires the use of a material exhibiting the dual properties of high tensile strength for barrel protection and high ductility for proper obturation is substantially satisfied by the unique laminated pocket portion of the improved composite shot wad structure of the above cross-referenced patent application. The laminated pocket portion has an inner liner of tough, high tensile strength material, such as nylon, and an outer body of soft, low tensile strength material, such as polyethylene, which also composes the remainder of the wad structure. On the one hand, the tough, high tensile strength inner liner adapts the pocket portion to withstand the radially-directed compressive forces generated by acceleration of hard shot, such as steel or tungsten shot, in the barrel of a shotgun. The hard shot is prevented from penetrating the pocket portion sidewall and coming in contact with and marring the shotgun barrel. On the other hand, the soft, low tensile strength outer body adapts the wad structure to obturate effectively.
While the composite shot wad structure with the unique laminated pocket portion of the above cross-referenced application protects the shotgun barrel without sacrificing obturation capacity, it lacks flexibility in loading in that it will only accommodate one load size. This shortcoming makes it necessary to manufacture several sizes of wad structures with different volumes of loading capacity which increases manufacturing costs.
One attempt to accommodate a range of load sizes in one shot wad structure is illustrated and described in U.S. Pat. No. 3,788,224 to Merritt. Basically, a longer shot protector cup telescopes at its lower end into an upper mouth of a shorter sealing overpowder cup to provide a variable volume within the shotshell. The two cups tend to trap air between them, or, alternatively, the shorter cup incorporates a center post, which resists telescoping of the longer cup into the shorter one. Thus, stresses are built into the shot wad structure which increase in proportion to the increase in the volume of the shot loading capacity of the longer cup as the latter is forced further down into the shorter cup. While this relationship may have some benefits in terms of reducing shot deformation when soft lead shot is used, hard steel shot does not deform and so building in stresses would merely increase the complexity of the steps required in assembling the lower end of the longer cup into the mouth of the shorter cup. Furthermore, since both of the partially telescoped cups are made from the same relatively soft plastic material, the shot wad structure of this patent is not adapted to prevent penetration of the hard steel shot through the sidewall of the longer cup and thus would fail to protect the shotgun barrel.
Consequently, a need exists to come up with a solution which will overcome the problems of sidewall penetration and shotgun barrel marring by hard shot and of inadequate flexibility in shot loading capacity, while at the same time be one which is workable and economical in the sense that it takes advantage of conventional high-speed automatic assembling techniques.